Tekpower TP3711A Programmable DC Electronic Load, 300 Watts with Part To Mount to a Rack

It wasnt calibrated as it said! calibration is expired!!!

A great load, especially considering the price. We've got several of the 150W and 300W models some of them are 7 years old. They are frequently run for days on end at about 50% capacity. The only issue I've ever had was with the fan "grill" on the bottom of the unit getting pushed into the fan; it makes a racket when the fan kicks on but it's easily fixed.

This electronic load will satisfy some relatively simple needs and it is certainly less costly than the B&K 8500 or 8600 loads. The front panel controls are OK but the curved buttons are not to my liking (I don't like this feature on my Rigol DP832 either). The accuracy is good but does not fully meet the specifications cited. But the description of the product is misleading in a couple of significant ways.First, the software and included USB -->TTL level interface cannot work with either Windows 8.1 or Windows 10. Yes, I know that some will say that Windows 7 32 bit is the best OS to use but in many cases, including mine) I didn't have that choice. The manufacturer cannot supply a version of software that can work with Windows versions newer than Win 7/32 bit. As incredible as it seems, they actually suggested I buy a 3rd party non-isolated RS-232 to USB dongle to use. Guess they didn't read their own manual or understand the importance of isolation in lab equipment.Second is the fact that you are likely to get old stock. I think this load is not a big seller and mine arrived with a calibration certificate way out of date. The rep said this was a "paperwork" problem and said the factory would fix it. I guess by "fix" they mean to change the date and send it back. Note my earlier comment that this load was not in compliance with the published specifications so the idea of calibration seems to be somewhat flexible for Tekpower.Taken together this means that the load is not programmable (at least by computer) and it does not meet specs. Critical flaws for my use but if you need something to soak up 300 W and can use other test equipment for voltage and current, this will get the job done. I returned mine to Amazon and got the B&K. Very happy with that so far.

NOTE: I noticed that Amazon's automatically placed product photo that accompanies my review shows the TekPower model TP3723A, which is a very different device than the TP3711A that I am reviewing. On February 18, 2016, I contacted Amazon customer service and sent them a screen shot to show them what I was seeing. Hopefully they will figure out how to get the correct photo at appear. But please be aware that the photo shown MIGHT still be incorrect as you read this. If it the photo shows an orange-ish display, it is the wrong photo (the TP3711 has a green-ish display).I often get involved in custom electronic design jobs that involve power supplies and/or batteries. Many are LED constant current supplies. Being able to accurately regulate current from a power supply, or test a supply or battery, can greatly simplify the design work, especially when empirical procedures/experiments are involved. All of my bench power DC supplies have current limiting, but coming up with a test load can be difficult at times.....I can wire a bunch of resistors together, or rig up some power transistors with negative feedback, but that always takes time and is distracting from the main design process. The common solution for all of this is of course a DC Electronic Load.The concept of the DC Electronic Load is simple, and indeed a person can make a basic one for not too many dollars, and schematic diagrams are readily available online. But I decided that I wanted mine to handle at least 150 Watts, AND have accurate metering of current and voltage, AND have constant current mode PLUS constant resistance mode AND constant power mode (both of the latter are just different ways of using the DC same load), I realized that I would need not only the basic electronics but also an intelligent (i.e. microprocessor based) front end, precision shunt resistors, and big heatsinks and adjustable fans. All of this would cost me at least $300 in parts, plus many hours of design time, procurement of a case/chassis, design and fabrication of the front end, etc. It started to look like a big job, and a time consuming one.I started to look at off-the-shelf DC Loads, with attention to reasonably priced ones that would not break the bank. It seems that pretty much all of the DC Electronic Loads out there, at least those under a certain power rating, are made by two companies in Taiwan, and those are then brand labeled for all sorts of companies in the States, Asia, Europe, etc. I found out that the several B&K Precision DC Loads, for example, and all made by one of the those companies in Taiwan.I read lots of blogs where people have investigated these things, and the general upshot is that many different DC Loads use the same electronic designs for the load itself, and then different looking cases and programmable front ends are built around those basic designs. It seems that the Taiwanese company "Array" makes a ton of well received DC Loads, and those are sold under many brand names, one of which is Tekpower.I did NOT want to buy some low priced 'Chinese' device that would have no warranty or technical support. So I started looking for a company in the States that sold some version of the Array-made DC Loads, and the qualifying company would be one that I could easily get on the phone, talk to a technician without much trouble, and get prompt responses to emails. The Tekpower brand is supported by a California company that also supports numerous other brands originating in China or Taiwan. It turns out that I already have some other products that they support.I decided originally on the identical-looking TP3710A, which is a 150W model, but when I saw that I could get the TP3711A (with its 300W rating) for only $100 more, I decided to buy the more capable model. The two are identical other than their power rating.So far I am quite pleased with my DC Load. I opened the case and saw that the construction looks to be of good quality....not as good as HP/Agilent, but still quite good. Nice PC boards, neat wiring, good soldering, good-looking components. The display is clear and the user interface is fairly intuitive. I have used it so far to test the Watt-hours of some rechargeable batteries, and to calibrate the adjustments and meters on a lab power supply. I also used it to test some LED chips for a lighting project.There are two internal power banks which work in parallel. I assume that the TP3710A has only one such power bank. Each power bank has several power transistors mounted on a large heatsink. Each power bank has a fan on the bottom of the case, and another fan on the rear of the case. So there are a total of four fans on this Load. The fans appear to turn on and off, and automatically adjust their speed, as required to keep the heatsinks cool.There are three gray buttons for selecting Constant Current, Constant Resistance, and Constant Power modes. Once a mode is selected, you can either enter the desired current, resistance or power using the white buttons of the numeric keypad, or you can spin the big knob on the front panel. If you use the knob, there are two adjacent cursor buttons which allow you to influence the value being adjusted from different orders of magnitude. For example, you can adjust one digit of the value, then move the cursor and adjust a different digit. But if you adjust a digit so that it rolls over from 9 to 0 or 0 to 9, the values automatically 'carry' to adjacent digits like an odometer. This is quick and intuitive, and more useful when you want to slowly tweak values during experiments.I have a couple small gripes with this product:- It is an older design, dating from when RS-232 was still a common computer interface, and that RS-232 port on the back is the only way to interface this DC Load with a computer (for monitoring and for automating the load's adjustments). TekPower does bundle this Load with an RS-232 to USB adapter, which they claim also provides Galvanic isolation between Load and computer.- They also provide an unmarked DC-ROM with some basic software for your computer, Their tech support told me that it works best with older versions of Windows, but that they had not done much testing with newer versions of Windows. I was advised to use Windows XP if I had it available. I have not made any attempt so far to test the USB interface or the software.- The Load comes with detachable front handles that might help to handle it in certain mounting situations. It does NOT come with a rack mounting kit. If you don't attach the handles, there is a sort of ugly blank area on each side of the Load just behind the front bezel. There are side handles, which would probably never be useful.I have NOT used either the USB adapter or the included software, so I cannot comment in that regard.

People think that this TekPower 3711A is the rebranded version of Array 3711A electronic load tester. I thought so too, until I did a basic teardown of the unit.The unit uses cheapo thermister temperature sensors. The fans are always on, making it a bit annoying, even though the speed "varies". There is no reverse polarity protection, though it was advertised as having such feature. The PC software came with it is garbage; it's basically a hit or miss !! Battery discharger app almost never work. The "dynamic load" programming isn't very useful either.The pros are current reading within specs, 360V and 300W rating. That's all I can think of...In short, this electronic load is basically a very old version, heavily stripped down version of the Array 3711A. I think that is how TekPower made money from rebranding. It stripped down the hardware components; but still uses Array's specs/datasheet, which is quite misleading imho. Like the other reviewer said, it's an okay unit for basic testing in a standanone setting. Bewared that this is an old/outdated stripped down version and that you are unlikely to receive a pure rebranded version !!